A composition containing a glycerol alkyl ether of the general formula R-O-CH2-CHOH-CH2OH in which R is a C3-C18 alkyl group, the alkyl group branched or unbranched, unsubstituted or substituted by one or more hydroxyl, one or more C1-C4 alkoxy groups, or both one or more hydroxyl and one or more C1-C4 alkoxy groups, and the C3-C18 alkyl group, whether branched or unbranched, unsubstituted or substituted, is optionally interrupted by up to four oxygen atoms, and one or more compound selected from general formula (II), in which each of R1-R10 is independently selected from hydrogen, hydroxyl, alkyl hydroxyl, alkoxy, alkyl ether, alkyl ester and glycoside, wherein the alkyl, the alkoxy and the alkyl portion of the alkyl ester contains from 1 to 4 carbon atoms, branched or unbranched, and the ester of the alkyl ester contains from 1 to 5 carbon atoms, branched or unbranched.
